Bad Air Days in Natrona County, Wyoming: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 521 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (42% particle days).

When the bad days come in Natrona

Most bad days here fall in July and August and September. Averaged over 2016 to 2025.

What to buy, and what not to

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

The worst days on file

The worst recent year was 2021, with 6 bad days on 365 monitored days.

Date	AQI	Main pollutant
2017-09-03	137	PM2.5
2024-07-23	136	Ozone
2024-08-22	130	PM2.5
2021-08-31	125	PM2.5
2020-09-17	124	PM2.5

Most days, not the worst ones

Across 3,652 monitored days from 2016 to 2025, the air in Natrona County rated Good on 84% of them, more often than the 72% typical of monitored counties, and Moderate on 15%. The median day sat at AQI 42; one day in ten went above 57.

The pollutant setting the AQI on an ordinary day here:

ozone93%3,406 days
fine particles (PM2.5)6%205 days
nitrogen dioxide1%41 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Median AQI	Highest AQI
2025*	365	315	50	0	42	76
2024	366	282	78	6	43	136
2023	365	344	20	1	42	102
2022	365	317	48	0	42	97
2021	365	282	77	6	42	125
2020	366	316	46	4	42	124
2019	364	327	37	0	42	74
2018	365	286	79	0	42	90
2017	365	286	77	2	44	137
2016	366	330	36	0	41	80
2015	365	329	36	0	41	96
2014	365	327	38	0	41	77
2013	365	301	62	2	42	133
2012	365	307	57	1	31	103
2011	212	176	36	0	33	77
2010	121	111	10	0	22	60

*2025 may be a partial year in EPA's file.

Wyoming compared

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.